Telomeres and telomerase in T cells of tumor immunity

Maternal testosterone affects offspring telomerase activity in a long-lived seabird

Androgens are a group of steroid hormones that have long been proposed as a mechanism underpinning intergenerational plasticity. In birds, maternally allocated egg testosterone, one of the main androgens in vertebrates, affects a wide variety of offspring phenotypic traits but the mechanisms underlying this form of intergenerational plasticity are not yet well understood. Recent in vitro and animal model studies have shown that telomerase expression and activity are important targets of androgen signaling. The telomerase enzyme is known for its repair function on telomeres, the DNA-protein complexes at the ends of chromosomes that are involved in genomic integrity and cell aging. However, the role of maternal testosterone in influencing offspring telomerase levels in natural populations and its consequences on telomere length and potentially on offspring development is still unknown. Here, by experimentally modifying the level of egg testosterone in a natural population of yellow-legged gull (Larus michahellis), we show that chicks hatched from testosterone-treated eggs had higher average levels of telomerase and faster growth than controls during the first week of life. While testosterone-treated chicks also tended to have longer telomeres than controls at hatching this difference disappeared by day 6 of age. Overall, our results suggest that maternal testosterone may have a potential adaptive value by promoting offspring growth and presumably telomerase levels, as this enzyme plays other important physiological functions (e.g., stress resistance, cell signaling, or tissue genesis) besides telomere lengthening. Nonetheless, our knowledge of the potential adaptive function of telomerase in natural populations is scarce and so the potential pathways linking maternal hormones, offspring telomerase, and fitness should be further investigated.

Association of Intrauterine Microbes with Endometrial Factors in Intrauterine Adhesion Formation and after Medicine Treatment

Intrauterine adhesions (IUAs) have caused serious harm to women’s reproductive health. Although emerging evidence has linked intrauterine microbiome to gynecological diseases, the association of intrauterine microbiome with IUA, remains unknown. We performed metagenome-wide association, metabolomics, and transcriptomics studies on IUA and non-IUA uteri of adult rats to identify IUA-associated microbial species, which affected uterine metabolites and endometrial transcriptions. A rat model was used with one side of the duplex uterus undergoing IUA and the other remaining as a non-IUA control. Both 16S rRNA sequencing and metagenome-wide association analysis revealed that instead of Mycoplasmopsis specie in genital tract, murine lung pathogen Mycoplasmopsispulmonis markedly increased in IUA samples and displayed a distinct positive interaction with the host immune system. Moreover, most of the IUA-enriched 58 metabolites positively correlate with M.pulmonis, which inversely correlates with a mitotic progression inhibitor named 3-hydroxycapric acid. A comparison of metabolic profiles of intrauterine flushing fluids from human patients with IUA, endometritis, and fallopian tube obstruction suggested that rat IUA shared much similarity to human IUA. The endometrial gene Tenascin-N, which is responsible for extracellular matrix of wounds, was highly up-regulated, while the key genes encoding parvalbumin, trophectoderm Dkkl1 and telomerase involved in leydig cells, trophectoderm cells, activated T cells and monocytes were dramatically down-regulated in rat IUA endometria. Treatment for rat IUA with estrogen (E2), oxytetracycline (OTC), and a traditional Chinese patent medicine GongXueNing (GXN) did not reduce the incidence of IUA, though inflammatory factor IL-6 was dramatically down-regulated (96–86%) with all three. Instead, in both the E2 and OTC treated groups, IUA became worse with a highly up-regulated B cell receptor signaling pathway, which may be associated with the significantly increased proportions of Ulvibacter or Staphylococcus. Our results suggest an association between intrauterine microbiota alterations, certain uterine metabolites, characteristic changes in endometrial transcription, and IUA and the possibility to intervene in IUA formation by targeting the causal factors, microbial infection, and Tenascin-like proteins.

In vivo and in vitro inhibition of SCLC by combining dual cancer-specific recombinant adenovirus with Etoposide

PURPOSE

Oncolytic virotherapy is emerging as an important modality in cancer treatment. In a previous study, we designed and constructed Ad-Apoptin-hTERTp-E1a (Ad-VT), a dual cancer-selective anti-tumor recombinant adenovirus.

METHODS

To explore the therapeutic effect of recombinant adenovirus Ad-VT together with Etoposide on small cell lung cancer, the ability of Ad-VT alone, Etoposide alone, and a combination of Ad-VT + Etoposide to inhibit proliferation of NCI-H446 and BEAS-2B cells was investigated using the WST-1 method. According to the inhibitory action of different combinations, a combination index (CI) was estimated by CalcuSyn software to select the best combination. The inhibitory effect of Ad-VT combined with Etoposide on NCI-H446 and BEAS-2B cells was detected by crystal violet staining and the CFST method. Hoechst, Annexin V and JC-1 staining were used to explore the inhibitory pathway of Ad-VT combined with Etoposide on NCI-H446 cells. The migratory and invasive abilities of treated NCI-H446 cells were assessed by Transwell and BioCat methods. Tumor volume, body weight and survival rate were measured to analyze the anti-tumor and toxic effects of different treatments in tumor-bearing mice.

RESULTS

Ad-VT (20 MOI) combined with Etoposide (400 nM) significantly inhibited NCI-H446 cell proliferation with reduced toxicity of Etoposide to normal cells. Ad-VT induced apoptosis of NCI-H446 cells mainly through the mitochondrial apoptosis pathway, an effect significantly increased by the combined treatment. Ad-VT together with Etoposide significantly inhibited migration and invasion of NCI-H446 cells, inhibited tumor growth in vivo and prolonged the survival of tumor-bearing mice.

CONCLUSIONS

The above results indicate that when combined with Etoposide, Ad-VT may have an important role in synergistically inhibiting tumors.

Immune Aging and Immunotherapy in Cancer

Immune functions decline as we age, while the incidence of cancer rises. The advent of immune checkpoint blockade (ICB) has not only revolutionized cancer therapy, but also spawned great interest in identifying predictive biomarkers, since only one third of patients show treatment response. The aging process extensively affects the adaptive immune system and thus T cells, which are the main target of ICB. In this review, we address age-related changes regarding the adaptive immune system with a focus on T cells and their implication on carcinogenesis and ICB. Differences between senescence, exhaustion, and anergy are defined and current knowledge, treatment strategies, and studies exploring T cell aging as a biomarker for ICB are discussed. Finally, novel approaches to improve immunotherapies and to identify biomarkers of response to ICB are presented and their potential is assessed in a comparative analysis.

Association of strong risk of hTERT gene polymorphic variants to malignant glioma and its prognostic implications with respect to different histological types and survival of glioma cases

BACKGROUND

Germline genetic variants of human telomerase reverse transcriptase (hTERT) are known to predispose for various malignancies, including glioma. The present study investigated genetic variation of hTERT T/G (rs2736100) and hTERT G/A (rs2736098) with respect to glioma risk.

METHODS

Confirmed cases (n = 106) were tested against 210 cancer-free healthy controls by the polymerase chain reaction-restriction fragment length polymorphism technique for genotyping.

RESULTS

Homozygous variant 'GG' genotype of rs2736100 frequency was > 4-fold significantly different in cases versus controls (39.6% 17.2%; p < 0.0001). Furthermore, variant 'G' allele was found to be significantly associated with cases (0.5 versus 0.2 in controls; p < 0.0001). Homozygous variant rs2736098 'AA' genotype (35.8% versus 23.8%) and allele 'A' (0.49 versus 0.34) showed a marked significant difference in cases and controls, respectively (p < 0.05). In hTERT rs2736100, the GG genotype significantly presented more in higher grades and GBM (p < 0.0001). Furthermore, the GG variant of hTERT rs2736100 had a poor probability with respect to the overall survival of patients compared to TG and TT genotypes (log rank p = 0.03). Interestingly, two haplotypes of hTERT rs2736100/rs2736098 were identified as GG and GA that conferred a > 3- and 5-fold risk to glioma patients respectively, where variant G/A haplotype was observed to have the highest impact with respect to glioma risk (p < 0.0001).

CONCLUSIONS

The results of the present study indicate that hTERT rs2736098 and rs2736100 variants play an important role in conferring a strong risk of developing glioma. Furthermore, hTERT rs2736100 GG variant appears to play a role in the bad prognosis of glioma patients. Haplotypes GG and GA could prove to be vital tools for monitoring risk in glioma patients.

Chemovirotherapy of Lung Squamous Cell Carcinoma by Combining Oncolytic Adenovirus With Gemcitabine

Oncolytic virotherapy is emerging as an important agent in cancer treatment. In a previous study, we designed and constructed Ad-Apoptin-hTERTp-E1a (Ad-VT), a dual cancer-selective anti-tumor recombinant adenovirus. In this study, crystal violet staining and WST-1 assays showed that Ad-VT has a significant tumor killing effect in a time and dose dependent manner. The combination of Ad-VT (10 MOI) and gemcitabine (10 nM) significantly inhibited NCI-H226 cells, but did not increase the killing effect of gemcitabine on human normal bronchial epithelial cells BEAS-2B. Hoechst, JC-1 and Annexin V experiments demonstrated that the combination of Ad-VT and gemcitabine mainly inhibited NCI-H226 cell proliferation by inducing apoptosis (mitochondrial pathway). The combination also significantly inhibited the migration and invasion abilities of NCI-H226 cells. In vivo, Ad-VT in combination with low-dose gemcitabine could effectively inhibit tumor growth and prolong survival of mice. Ad-VT has the characteristics of tumor-selective replication and killing, in vitro and in vivo. The combined application of Ad-VT and gemcitabine has a synergistic effect, which can increase the anti-tumor effect and reduce the toxicity of chemotherapy drugs, indicating that Ad-VT has a potential clinical value in the treatment of lung squamous cell carcinoma.

A positive feedback loop between Wnt/β-catenin signaling and hTERT regulates the cancer stem cell-like traits in radioresistant nasopharyngeal carcinoma cells

Radioresistance may be induced by cancer stem cells (CSCs), while the biological traits of CSCs need to be retained by telomerase. The telomerase activity mainly depends on the transcriptional regulation of human telomerase reverse transcriptase (hTERT). Moreover, Wnt/β-catenin signaling is also considered essential for maintaining the CSC phenotypes. In the previous study, we discovered that the radioresistant nasopharyngeal carcinoma cells CNE-2R displayed CSC-like traits, as well as high expression of hTERT and β-catenin, but whether hTERT and β-catenin were involved in regulating the CSC-like traits and radiosensitivity of CNE-2R cells remained unclear. In this study, our results suggested that hTERT could positively regulate the expression of CSC-related proteins, as well as the cytoplasm- and nucleus-β-catenin, but it could not markedly regulate the expression of total β-catenin in CNE-2R cells. Meanwhile, Wnt/β-catenin signaling had a positive regulatory effect on the expression of hTERT and CSC-related proteins. Moreover, there was a β-catenin/hTERT protein complex in CNE-2R cells, indicating that β-catenin could directly interact with hTERT protein. Our results also revealed that silencing hTERT or suppressing Wnt/β-catenin signaling could attenuate telomerase activity and radioresistance of CNE-2R cells; while suppressing Wnt/β-catenin signaling, the telomerase activity and radioresistance could be reversed through overexpressing hTERT. Taken together, we have outlined a positive feedback loop between Wnt/β-catenin signaling and hTERT in CNE-2R cells, which can regulate the telomerase activity and CSC-like traits, thus regulating the radiosensitivity. Therefore, blocking Wnt/β-catenin signaling transduction and interfering with hTERT expression may be a promising approach for targeting radioresistant nasopharyngeal carcinoma cells with CSC-like traits.

DNA Hypermethylation Downregulates Telomerase Reverse Transcriptase (TERT) during H. pylori-Induced Chronic Inflammation

Helicobacter pylori infection causes chronic gastritis and is the major risk factor of gastric cancer. H. pylori induces a chronic inflammation-producing reactive oxygen species (ROS) which is a source of chromosome instabilities and contributes to the development of malignancy. H. pylori also promotes DNA hypermethylation, known to dysregulate essential genes that maintain genetic stability. The maintenance of telomere length by telomerase is essential for chromosome integrity. Telomerase reverse transcriptase (TERT) is the catalytic component of telomerase activity and an important target during host-pathogen interaction. We aimed to investigate the consequences of H. pylori on the regulation of TERT gene expression and telomerase activity. In vitro, hTERT mRNA levels and telomerase activity were analysed in H. pylori-infected human gastric epithelial cells. In addition, C57BL/6 and INS-GAS mice were used to investigate the influence of H. pylori-induced inflammation on TERT levels. Our data demonstrated that, in vitro, H. pylori inhibits TERT gene expression and decreases the telomerase activity. The exposure of cells to lycopene, an antioxidant compound, restores TERT levels in infected cells, indicating that ROS are implicated in this downregulation. In vivo, fewer TERT-positive cells are observed in gastric tissues of infected mice compared to uninfected, more predominantly in the vicinity of large aggregates of lymphocytes, suggesting an inflammation-mediated regulation. Furthermore, H. pylori appears to downregulate TERT gene expression through DNA hypermethylation as shown by the restoration of TERT transcript levels in cells treated with 5′-azacytidine, an inhibitor of DNA methylation. This was confirmed in infected mice, by PCR-methylation assay of the TERT gene promoter. Our data unraveled a novel way for H. pylori to promote genome instabilities through the inhibition of TERT levels and telomerase activity. This mechanism could play an important role in the early steps of gastric carcinogenesis.

Predictive and prognostic significance of telomerase levels/telomere length in tissues and peripheral blood in head and neck squamous cell carcinoma

A growing body of evidence indicates that the expression of TERT, the catalytic subunit of telomerase, is a biological marker of progression in several cancers. We investigated the predictive and prognostic role of TERT levels and telomere length in tissues and peripheral blood in patients with head and neck squamous cell carcinoma (HNSCC). High TERT levels in cancer tissues were independently associated with worse response to therapy (odds ratio [OR]:6.26), regional failure (hazard ratio [HR]:5.75), progression (HR:2.12), and death (HR:3.53). Longer telomeres in the mucosa surrounding the tumor (SM) were independently associated with a lower risk of mucosal failure (HR:0.39). While telomere length in peripheral blood mononuclear cells (PBMC) significantly decreased with age, no correlation was found between age and telomere length in SM. No associations were found between TERT levels in plasma and telomere length in PBMC and the prognostic variables. High levels of TERT transcripts in cancer cells represent a reliable prognostic marker for identifying HNSCC patients with risk of progression. The altered relationship of telomere length to age in SM compared with PBMC suggests that in a subset of cases the phenotypically normal SM constitutes an acquired telomere-shortened epithelial field prone to genetic instability.

The prognostic significance of hTERT overexpression in cancers: A systematic review and meta-analysis

BACKGROUND

Human telomerase reverse transcriptase (hTERT) plays an important role in cancer progression. Recently, several clinical studies investigated how the overexpression of hTERT predicts the poor prognosis of solid tumors. However, the results were inconclusive, partly because of the small numbers of patients included.

METHOD

We systematically searched PubMed, Web of Science, and Embase to identify relevant studies until August 2017. Hazard ratios (HRs) with 95% confidence intervals (CIs) were used to evaluate the association of hTERT expression and survival outcomes.

RESULTS

A total of 27studies enrolling 2530 solid tumor patients were included in this meta-analysis. There were strong significant associations between hTERT overexpression and all endpoints: overall survival (OS) (HR = 1.50, 95% CI: 1.31-1.73, P = .00), disease-free survival (HR = 1.84, 95% CI: 1.38-2.46; P = .00), and recurrence-free survival (HR = 1.79, 95% CI: 1.07-2.99; P = .028). In the subgroup analysis, it was found that the overexpression of hTERT induced poor OS in lung cancer (HR = 1.51, 95% CI: 1.21-1.89; P = .00).

CONCLUSION

Our comprehensive systematic review concluded that the overexpression of hTERT was associated with poor survival in human solid tumors. hTERT may be a valuable predictive biomarker for prognosis.

Association of MNS16A VNTR and hTERT rs2736098: G>A polymorphisms with susceptibility to diffuse large B-cell lymphoma

PURPOSE

Genetic studies of diffuse large B-cell lymphoma (DLBCL) may serve to clarify disease pathogenesis and mark at-risk populations. Evidence of long telomeres and high telomerase activity have been demonstrated in DLBCL. We aimed to examine human telomerase gene ( hTERT) MNS16A variable number of tandem repeats and hTERT rs2736098: G>A polymorphisms in relation to DLBCL susceptibility.

METHODS

In a case control study, 71 patients with DLBCL and 156 controls were genotyped for MNS16A using polymerase chain reaction and hTERT rs2736098: G>A using polymerase chain reaction restriction fragment length polymorphism.

RESULTS

In both codominant and recessive models, there was a significant difference in the distribution of MNS16A genotypes between patients with DLBCL and controls (p = 0.047 and p = 0.018, respectively). In both models, carriers of S/S genotype were at higher risk to develop DLBCL (odds ratio [OR] 2.51, 95% confidence interval [CI] 1.19-5.29 and OR 2.19, 95% CI 1.15-4.17, respectively). In the log-additive model, each copy of S allele significantly increased DLBCL risk in an additive form (p = 0.018, OR 1.57, 95% CI 1.08-2.29). The frequency distribution of MNS16A S alleles was significantly higher in patients than controls (p = 0.012). Carriers of S alleles were at higher risk to develop DLBCL than carriers of L alleles (OR 1.67, 95% CI 1.12-2.49). hTERT rs2736098: G>A genotype distribution did not differ significantly between patients with DLBCL and controls.

CONCLUSIONS

MNS16A genetic variations are associated with DLBCL susceptibility.

Trial watch: DNA-based vaccines for oncological indications

DNA-based vaccination is a promising approach to cancer immunotherapy. DNA-based vaccines specific for tumor-associated antigens (TAAs) are indeed relatively simple to produce, cost-efficient and well tolerated. However, the clinical efficacy of DNA-based vaccines for cancer therapy is considerably limited by central and peripheral tolerance. During the past decade, considerable efforts have been devoted to the development and characterization of novel DNA-based vaccines that would circumvent this obstacle. In this setting, particular attention has been dedicated to the route of administration, expression of modified TAAs, co-expression of immunostimulatory molecules, and co-delivery of immune checkpoint blockers. Here, we review preclinical and clinical progress on DNA-based vaccines for cancer therapy.

hTERT promotes the invasion of gastric cancer cells by enhancing FOXO3a ubiquitination and subsequent ITGB1 upregulation

BACKGROUND AND AIMS

Human telomerase reverse transcriptase (hTERT) plays an important role in cancer invasion, but the relevant mechanism is not well known. This study aims to investigate the role and mechanism of hTERT in gastric cancer metastasis.

DESIGN

Proteomics analysis, qPCR and western blotting were used to screen for hTERT-regulated candidate molecules in gastric cancer invasion. Chromatin immunoprecipitation (ChIP) qPCR was performed to identify the binding sites of hTERT at the regulatory region of the integrin β1 (ITGB1) gene. ChIP assays were further applied to elucidate the transcription factors that bound to the regulatory region. The interactions between hTERT and the transcription factors were tested by co-immunoprecipitation (Co-IP) and glutathione S-transferase (GST) pull-down experiments. Moreover, the revealed pathway was verified in tumour-bearing nude mice and human gastric cancer tissues.

RESULTS

ITGB1 was identified as a downstream gene of hTERT, and there were two hTERT-binding regions within this gene. hTERT alleviated the binding of forkhead box O3 (FOXO3a) to FOXO3a binding element (+9972∼+9978), but it enhanced the binding of forkhead box M1 (FOXM1) to FOXM1 binding element (-1104∼-1109) in ITGB1 gene. Importantly, FOXO3a played a major role in hTERT-induced ITGB1 expression, and the hTERT/murine double minute 2 (MDM2) complex promoted the ubiquitin-mediated degradation of FOXO3a. Moreover, hTERT increased ITGB1 expression in xenograft gastric cancer, and the level of hTERT was positively correlated with that of ITGB1 in human gastric cancer tissues.

CONCLUSIONS

The hTERT/MDM2-FOXO3a-ITGB1 pathway markedly contributes to hTERT-promoted gastric cancer invasion, suggesting that this pathway might be a novel target for the prevention and treatment of gastric cancer metastasis.

A Natural Product Telomerase Activator Lengthens Telomeres in Humans: A Randomized, Double Blind, and Placebo Controlled Study

TA-65 is a dietary supplement based on an improved formulation of a small molecule telomerase activator that was discovered in a systematic screening of natural product extracts from traditional Chinese medicines. This study summarizes the findings on telomere length (TL) changes from a randomized, double blind, placebo controlled study of TA-65 over a 1 year period. The study was conducted on 117 relatively healthy cytomegalovirus-positive subjects aged 53–87 years old. Subjects taking the low dose of TA-65 (250 U) significantly increased TL over the 12 months period (530 ± 180 bp; p = 0.005), whereas subjects in the placebo group significantly lost TL (290 ± 100 bp; p = 0.01). The high dose of TA-65 (1000 U) showed a trend of improvements in TL compared with that of the placebo group; however, the improvements did not reach statistical significance. TL changes in the low-dose group were similar for both median and 20th percentile TLs. The findings suggest that TA-65 can lengthen telomeres in a statistically and possibly clinically significant manner.

Correlation between the expression of hTERT gene and the clinicopathological characteristics of hepatocellular carcinoma

The aim of the present study was to detect the expression levels of the human telomerase reverse transcriptase (hTERT) gene in hepatocellular carcinoma (HCC), and investigate its significance in the incidence and development of the cancer. HCC tissues and corresponding para-carcinoma liver tissues were surgically collected from 78 patients with HCC who presented to Shandong Provincial Hospital (Jinan, Shandong, China). hTERT expression at the protein and mRNA levels were detected by immunohistochemistry (streptavidin peroxidase method) and reverse transcription polymerase chain reaction, respectively, in the HCC tissues and corresponding para-carcinoma liver tissues of 78 HCC patients and in 12 samples of normal liver tissue. The data were analyzed using SPSS 17.0 statistical software, and employing χ² tests and t-tests. hTERT protein was mainly expressed in the HCC cell cytoplasm, but was occasionally observed in the cell nucleus. The positive rates of hTERT protein and mRNA expression in the HCC patients were 84.62% (66/78) and 78.21% (61/78), respectively, which was significantly higher compared with the rates of 10.26% (8/78) and 8.97% (7/78) in the paired para-carcinoma liver tissues (P<0.01). hTERT protein and mRNA were not expressed in the normal liver tissues (0/12). χ² test and t-test analysis revealed that hTERT gene expression was correlated with tumor grade, the presence/absence of a portal vein tumor thrombus, hepatitis B surface antigen positivity and a high α-fetoprotein level (P<0.05) rather than patient age, gender or tumor size. Expression of the hTERT gene may play a pivotal role in the incidence and development of HCC. The hTERT gene potentially serves as an important molecular and biological index for diagnosing and predicating the biological behavior of HCC.

LINE-1 induces hTERT and ensures telomere maintenance in tumour cell lines

A hallmark of cancer cells is an activated telomere maintenance mechanism, which allows prolonged survival of the malignant cells. In more than 80% of tumours, telomeres are elongated by the enzyme telomerase, which adds de novo telomere repeats to the ends of chromosomes. Cancer cells are also characterized by expression of active LINE-1 elements (L1s, long interspersed nuclear elements-1). L1 elements are abundant retrotransposons in the eukaryotic genome that are primarily known for facilitating aberrant recombination. Using L1-knockdown (KD), we show for the first time that L1 is critical for telomere maintenance in telomerase-positive tumour cells. The reduced length of telomeres in the L1-KD-treated cells correlated with an increased rate of telomere dysfunction foci, a reduced expression of shelterin proteins and an increased rate of anaphase bridges. The decreased telomere length was associated with a decreased telomerase activity and decreased telomerase mRNA level; the latter was increased upon L1 overexpression. L1-KD also led to a decrease in mRNA and protein expression of cMyc and KLF-4, two main transcription factors of telomerase and altered mRNA levels of other stem-cell-associated proteins such as CD44 and hMyb, as well as a corresponding reduced growth of spheroids. The KD of KLF-4 or cMyc decreased the level of L1-ORF1 mRNA, suggesting a specific reciprocal regulation with L1. Thus, our findings contribute to the understanding of L1 as a pathogenicity factor in cancer cells. As L1 is only expressed in pathophysiological conditions, L1 now appears to be target in the rational treatment of telomerase-positive cancer.

miR-19b regulates hTERT mRNA expression through targeting PITX1 mRNA in melanoma cells

Human telomerase reverse transcriptase (hTERT) plays a crucial role in cancer development. We previously identified paired-like homeodomain1 (PITX1) as an hTERT suppressor gene. However, the underlying mechanisms that are involved in the regulation of PITX1 remain unknown. Here, we report that the microRNA-19b (miR-19b) regulates hTERT expression and cell proliferation through inhibition of PITX1. Compared with normal melanocyte cells, miR-19b expression was higher in most melanoma cells and was accompanied by downregulation of PITX1. Moreover, overexpression of miR-19b inhibited PITX1 mRNA translation through a miR-19b binding site within the 3'UTR of the PITX1 mRNA. Our combined findings indicate the participation of miR-19b as a novel upstream effector of hTERT transcription via direct targeting of PITX1.

Association between hTERT polymorphisms and the risk of breast cancer in a sample of Southeast Iranian population

BACKGROUND

Breast cancer (BC) is considered to be one of the most important causes of death worldwide, and it affects the Iranian female population a decade earlier than female in other parts of the world. Human telomerase reverse transcriptase (hTERT) is a main subunit of the telomerase complex. MNS16A is located downstream of the hTERT gene and is recognized as the regulator of hTERT promoter activity. The aim of the present study was to access the possible impact of hTERT variants on BC risk in an Iranian population in southeast Iran.

METHODS

A total of 491 subjects including 266 BC patients and 225 healthy women participated in the study. Polymerase chain reaction (PCR) was used to genotype the MNS16A variable number of tandem repeats and 177 bp ins/del polymorphisms in the hTERT gene. PCR-RFLP and ARMS-PCR were used to genotype hTERT rs2736098 and 2735940, respectively. The association between genotypes and BC was assessed by computing the odds ratio (OR) and 95% confidence intervals (95% CI) from logistic regression analyses. A p-value of <0.05 was considered statistically significant.

RESULTS

The MNS16A genotype frequency distribution in BC patients was: LL, 43.2%; LS, 51.1%; and SS, 5.7%, and in controls: LL, 29.5%; LS, 68.3%; and SS, 2.2%. The LS genotype decreased the risk of BC compared with LL (OR=0.51, 95% CI=0.35-0.75, p<0.001). The hTERT 177 bp ins/del polymorphism was not polymorphic in our population. All subjects had the ins/ins genotype. Our findings indicate that the MNS16A genotype and hTERT rs2736098 variant were associated with BC risk in the study. We also showed that the rs2736098 A/G polymorphism increased the risk of BC (OR=1.80, 95% CI=1.12-2.88, p=0.017, AG vs AA; OR=1.80, 95% CI=1.06-3.06, p=0.033, GG vs AA; OR=1.87, 95% CI=1.19-2.94, p=0.006, AG+GG vs AA). No significant association was found between the rs2735940 C/T variant and BC.

CONCLUSION

Our findings indicate that the MNS16A genotype and the hTERT rs2736098 variant influence the risk of BC in an Iranian population in southeast Iran.